UNDERSTANDING THE COVERAGE RATE FOR REDGARD …

[Pages:2]TB94 UNDERSTANDING THE COVERAGE RATE FOR REDGARD LIQUID WATERPROOFING AND CRACK PREVENTION MEMBRANE

To simplify planning for and applying liquid waterproofing membranes, CUSTOM has updated its instructions for the application of RedGard? Waterproofing and Crack Prevention Membrane to a coverage rate (square feet per gallon) rather than application to a given wet film thickness.

Challenges with Measuring Wet Film Thickness Wet film thickness will vary on a jobsite depending on where the measurement is taken and how soon it is measured after the application of the waterproofing membrane. As soon as the product is applied, it begins to cure and lose water through evaporation. The longer the wait, the thinner the film gets, making it important to measure the wet film thickness immediately after the membrane is first applied. Wet film thickness ratings typically refer to the moment the membrane is applied.

In controlled laboratory conditions, an absolutely flat film can be metered out with no ridges, but in the field, there will be substrate irregularities and ridges from the application method with low and high points in the wet film. This creates questions about whether the low or high points should be measured, or if the results be can be averaged. Assessing coverage with more measurements will improve the chances that the proper amount of material is being applied.

Due to the prevalence of so many questions concerning correct measurement of the wet film thickness, the directions on CUSTOM's RedGard Liquid Waterproofing and Crack Prevention Membrane now provide an easy-to-follow coverage rate based on square footage. When a given area is uniformly coated with a full gallon of RedGard liquid membrane, the correct film thickness has been achieved. Since this is a mathematical absolute, there is no need to try to measure the wet film thickness.

This method can create a concern for an inspector of the installers' work if the inspector does not know how many gallons of membrane were used to cover an area. Then, the only recourse is to measure the dried film thickness of the waterproofing membrane with destructive testing.

Equating Coverage Rate to Film Thickness To help with the inspector's evaluation this chart compares the coverage rate in square feet per gallon with both the wet and dry film thickness of the

membrane. A single measurement of dry film thickness may not be indicative of other areas in the installation.

Multiple areas should be measured and averaged to determine actual application rate. The chart below can be used to determine the actual coverage rate, if the dry film or wet film thickness is known. The highlighted rates and thickness are the correct coverage rates for RedGard Liquid Waterproofing and Crack Prevention Membrane, depending on the need of the membrane.

RedGard Liquid Waterproofing and Crack Prevention Membrane Relationship of Coverage Rate to Wet and Dry Film Thickness (mils)

Coverage Sq Ft

per Gallon

Thickness Thickness

Wet

Dry

Requirement

mils

mils

12.8

125

74

15

107

63

20

80

47

Meet ANSI

25

64

38

A118.12

30

53

31

Meet ANSI

40

40

24

A118.10

50

32

19

General

55

29

17 Waterproofing

60

27

16

70

23

14

80

20

12

90

18

11

General Crack

100

16

10

Isolation

110

15

9

150

11

7.0

160

10

6.0

170

9.4

5.5

180

8.9

5.2

190

8.4

5.0

200

8.0

4.7

Technical Bulletin

Technical Services 800-282-8786

TB94 UNDERSTANDING THE COVERAGE RATE FOR REDGARD LIQUID WATERPROOFING AND CRACK PREVENTION MEMBRANE

Using a Mil Gauge to Measure Wet Film Thickness For installers who want to use a mil gauge to assess membrane coverage, CUSTOM provides the RedGard Thickness Gauge. Notched "teeth" representing mil depth appear on the face of the gauge, with microns on the reverse for use in metric measurement locations. Remove the blue coating and use as follows:

1. Hold the card at a 90 degree angle to the surface.

2. Press the teeth marked with the desired mil thickness into the fresh, wet RedGard.

3. Pull straight back to prevent adjacent product from clinging to the teeth.

4. Note the deepest tooth with RedGard on it as well as the next highest tooth that is not coated with RedGard.

5. The true RedGard mil thickness lies between these two readings.

6. Wipe the gauge with water after each use. 7. Readings should be repeated in different

areas and averaged to achieve the most accurate measurement of the mil thickness and ensure proper coverage. 8. Ensure that no voids or pinholes are left in the dried membrane from the testing process.

Consult the Custom Building Products website for more information on the correct application of RedGard, or contact CUSTOM's Technical Services Department at 800.282.8786.

The information in this bulletin is presented in good faith, but no warranty, express or implied, is given nor is freedom from any patent in as much as any assistance furnished by CUSTOM with reference to the safe use and disposal of its products provided without charge. Custom Building Products assumes no obligation or liability therefore, except to the extent that any such assistance shall be given in good faith.

TB94 3/17R

Technical Bulletin

Technical Services 800-282-8786

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